Car Dies when Brakes applied

I have a 1988 Grand Prix se 279000 miles. I hadn't driven it in about a month. When i went to start it, it was dead. I jump it and started just fine, idols just fine, it will shift in to gears just fine with brake applied. But when the jumper cables are off everything go just fine until i touch the brakes. When I do it dies immediately. I have no idea where to start. Thank you in advance.

An Autozone guy thought it had something to do with a vacume leak?? $80 part? does that sound right??

Sounds like a possible bad battery. If the battery is shorted, it's drawing all the reserve power from the system, and as soon as you add an electrical load (eg. brake lights), the car dies. Since the car has sat for some time, if you're in a cold weather area, the on-board electronics probably drained the battery and it froze, cracking the plates and shorting it out. Try a fresh battery first, if that doesn't fix it, let us know and we'll go from there.